Stabilization of liquid instabilities with ionized gas jets.

Impinging gas jets can induce depressions in liquid surfaces, a phenomenon familiar to anyone who has observed the cavity produced by blowing air through a straw directly above a cup of juice. A dimple-like stable cavity on a liquid surface forms owing to the balance of forces among the gas jet impingement, gravity and surface tension1,2. With increasing gas jet speed, the cavity becomes unstable and shows oscillatory motion, bubbling (Rayleigh instability) and splashing (Kelvin-Helmholtz instability)3,4. However, despite its scientific and practical importance-particularly in regard to reducing cavity instability growth in certain gas-blown systems-little attention has been given to the hydrodynamic stability of a cavity in such gas-liquid systems so far. Here we demonstrate the stabilization of such instabilities by weakly ionized gas for the case of a gas jet impinging on water, based on shadowgraph experiments and computational two-phase fluid and plasma modelling. We focus on the interfacial dynamics relevant to electrohydrodynamic (EHD) gas flow, so-called electric wind, which is induced by the momentum transfer from accelerated charged particles to neutral gas under an electric field. A weakly ionized gas jet consisting of periodic pulsed ionization waves5, called plasma bullets, exerts more force via electrohydrodynamic flow on the water surface than a neutral gas jet alone, resulting in cavity expansion without destabilization. Furthermore, both the bidirectional electrohydrodynamic gas flow and electric field parallel to the gas-water interface produced by plasma interacting 'in the cavity' render the surface more stable. This case study demonstrates the dynamics of liquids subjected to a plasma-induced force, offering insights into physical processes and revealing an interdependence between weakly ionized gases and deformable dielectric matter, including plasma-liquid systems.

ATAD5 functions as a regulatory platform for Ub-PCNA deubiquitination.

Ubiquitination status of proliferating cell nuclear antigen (PCNA) is crucial for regulating DNA lesion bypass. After the resolution of fork stalling, PCNA is subsequently deubiquitinated, but the underlying mechanism remains undefined. We found that the N-terminal domain of ATAD5 (ATAD5-N), the largest subunit of the PCNA-unloading complex, functions as a scaffold for Ub-PCNA deubiquitination. ATAD5 recognizes DNA-loaded Ub-PCNA through distinct DNA-binding and PCNA-binding motifs. Furthermore, ATAD5 forms a heterotrimeric complex with UAF1-USP1 deubiquitinase, facilitating the deubiquitination of DNA-loaded Ub-PCNA. ATAD5 also enhances the Ub-PCNA deubiquitination by USP7 and USP11 through specific interactions. ATAD5 promotes the distinct deubiquitination process of UAF1-USP1, USP7, and USP11 for poly-Ub-PCNA. Additionally, ATAD5 mutants deficient in UAF1-binding had increased sensitivity to DNA-damaging agents. Our results ultimately reveal that ATAD5 and USPs cooperate to efficiently deubiquitinate Ub-PCNA prior to its release from the DNA in order to safely deactivate the DNA repair process.

Inhibiting the Appearance of Green Emission in Mixed Lead Halide Perovskite Nanocrystals for Pure Red Emission.

Mixed halide perovskites exhibit promising optoelectronic properties for next-generation light-emitting diodes due to their tunable emission wavelength that covers the entire visible light spectrum. However, these materials suffer from severe phase segregation under continuous illumination, making long-term stability for pure red emission a significant challenge. In this study, we present a comprehensive analysis of the role of halide oxidation in unbalanced ion migration (I/Br) within CsPbI2Br nanocrystals and thin films. We also introduce a new approach using cyclic olefin copolymer (COC) to encapsulate CsPbI2Br perovskite nanocrystals (PNCs), effectively suppressing ion migration by increasing the corresponding activation energy. Compared with that of unencapsulated samples, we observe a substantial reduction in phase separation under intense illumination in PNCs with a COC coating. Our findings show that COC enhances phase stability by passivating uncoordinated surface defects (Pb2+ and I-), increasing the formation energy of halide vacancies, improving the charge carrier lifetime, and reducing the nonradiative recombination density.

Local Structures of Ex-Solved Nanoparticles Identified by Machine-Learned Potentials.

In this study, we identify the local structures of ex-solved nanoparticles using machine-learned potentials (MLPs). We develop a method for training machine-learned potentials by sampling local structures of heterointerface configurations as a training set with its efficacy tested on the Ni/MgO system, illustrating that the error in interface energy is only 0.004 eV/Å2. Using the developed scheme, we train an MLP for the Ni/La0.5Ca0.5TiO3 ex-solution system and identify the local structures for both exo- and endo-type particles. The established model aligns well with the experimental observations, accurately predicting a nucleation size of 0.45 nm. Lastly, the density functional theory calculations on the established atomistic model verify that the kinetic barrier for the dry reforming of methane are substantially reduced by 0.49 eV on the ex-solved catalysts compared to that on the impregnated catalysts. Our findings offer insights into the local structures, growth mechanisms, and underlying origin of the catalytic properties of ex-solved nanoparticles.

Photocatalytic Activation of Aryl(trifluoromethyl) Diazos to Carbenes for High-Resolution Protein Labeling with Red Light.

State-of-the-art methods in photoproximity labeling center on the targeted generation and capture of short-lived reactive intermediates to provide a snapshot of local protein environments. Diazirines are the current gold standard for high-resolution proximity labeling, generating short-lived aryl(trifluoromethyl) carbenes. Here, we present a method to access aryl(trifluoromethyl) carbenes from a stable diazo source via tissue-penetrable, deep red to near-infrared light (600-800 nm). The operative mechanism of this activation involves Dexter energy transfer from photoexcited osmium(II) photocatalysts to the diazo, thus revealing an aryl(trifluoromethyl) carbene. The labeling preferences of the diazo probe with amino acids are studied, showing high reactivity toward heteroatom-H bonds. Upon the synthesis of a biotinylated diazo probe, labeling studies are conducted on native proteins as well as proteins conjugated to the Os photocatalyst. Finally, we demonstrate that the conjugation of a protein inhibitor to the photocatalyst also enables selective protein labeling in the presence of spectator proteins and achieves specific labeling of a membrane protein on the surface of mammalian cells via a two-antibody photocatalytic system.

Simultaneous Detection of Infectious Diseases Using Aptamer-Conjugated Gold Nanoparticles in the Lateral Flow Immunoassay-Based Signal Amplification Platform.

Various platforms for the accurate diagnosis of infectious diseases have been studied because of the emergence of coronavirus disease (COVID-19) in 2019. Recently, it has become difficult to distinguish viruses with similar symptoms due to the continuous mutation of viruses, and there is an increasing need for a diagnostic method to detect them simultaneously. Therefore, we developed a paper-based rapid antigen diagnostic test using DNA aptamers for the simultaneous detection of influenza A, influenza B, and COVID-19. Aptamers specific for each target viral antigen were selected and attached to AuNPs for application in a rapid antigen diagnosis kit using our company's heterogeneous sandwich-type aptamer screening method (H-SELEX). We confirmed that the three viruses could be detected on the same membrane without cross-reactivity based on the high stability, specificity, and binding affinity of the selected aptamers. Further, the limit of detection was 2.89 pg·mL-1 when applied to develop signal amplification technology; each virus antigen was detected successfully in diluted nasopharyngeal samples. We believe that the developed simultaneous diagnostic kit, based on such high accuracy, can distinguish various infectious diseases, thereby increasing the therapeutic effect and contributing to the clinical field.

Nanosheet Particles with Defect-Free Block Copolymer Structures Driven by Emulsions Containing Crystallizable Surfactants.

Highly anisotropic-shaped particles with well-ordered internal nanostructures have received significant attention due to their unique shape-dependent photonic, rheological, and electronic properties and packing structures. In this work, nanosheet particles with cylindrical block copolymer (BCP) arrays are achieved by utilizing collapsed emulsions as a scaffold for BCP self-assembly. Highly elongated structures with large surface areas are formed by employing crystallizable surfactants that significantly reduce the interfacial tension of BCP emulsions. Subsequently, the stabilized elongated emulsion structures lead to the formation of BCP nanosheets. Specifically, when polystyrene-block-polydimethylsiloxane (PS-b-PDMS) and 1-octadecanol (C18-OH) are co-assembled within an emulsion, C18-OH penetrates the surfactant layer at the emulsion interface, lowering the interfacial tension (i.e., below 1 mN m-1 ) and causing emulsion deformation. In addition, C18-OH crystallization allows for kinetic arrest of the collapsed emulsion shape during solvent evaporation. Consequently, PS-b-PDMS BCPs self-assemble into defect-free structures within nanosheet particles, exhibiting an exceptionally high aspect ratio of over 50. The particle formation mechanism is further investigated by controlling the alkyl chain length of the fatty alcohol. Finally, the coating behavior of nanosheet particles is investigated, revealing that the deposition pattern on a substrate is strongly influenced by the particle's shape anisotropy, thus highlighting their potential for advanced coating applications.

Palladium-Catalyzed/Copper-Mediated Decarbonylative Cross-Coupling of S-Pyrimidyl Thioesters for Biaryl Synthesis.

A palladium-catalyzed/copper-mediated cross-coupling of S-pyrimidinyl thioesters with arylboronic acids to yield biaryls is described. The reaction is likely to proceed via cleavage of the S-C(O) bond and subsequent release of CO, rather than via cleavage of the S-C(pyrimidine) bond and release of SCO, as supported by the results of both experimental and computational studies. The investigation of the reaction scope with various S-pyrimidinyl thioesters and arylboronic acids showed that the reaction is significantly affected by the substituent of the thioester and the presence of a chelatable ortho substituent was found to increase reaction efficiency.

Psoas muscle area is associated with prognosis in elderly patients with hip fracture.

INTRODUCTION: Sarcopenia is a key predictor of prognosis in patients with hip fractures. This study utilized computed tomography (CT) scan (1) to determine the association between psoas muscle cross-sectional area (CSA) and mortality, along with other muscles, and (2) to confirm the correlation between muscle CSA and appendicular lean mass (ALM) measured using DXA in elderly patients with hip fracture. MATERIALS AND METHODS: Patients who were aged ≥ 50 years and underwent surgical treatment for hip fracture were eligible for this study. After a series of exclusion criteria, 217 female patients were included. Patient data, including clinical characteristics, such as body mass index (BMI), CSA, and ALM, were retrospectively collected. The Kaplan-Meier survival method and Cox proportional hazards regression analysis were used for the statistical analyses. The correlation between CSA/BMI and ALM was also assessed. RESULTS: Patients in the lowest quartile of psoas muscle CSA/BMI had shorter survival times than those in the other quartiles. When the Cox proportional hazards regression analysis was adjusted for multiple variables, the lowest quartile of the CSA/BMI of the psoas was a risk factor for mortality. The CSA/BMI of the psoas showed the highest correlation coefficient. The CSA/BMI ratio of the other muscles showed a moderately positive correlation with ALM. CONCLUSION: The CSA of the psoas is associated with prognosis in elderly patients with hip fractures and shows a moderately positive correlation with ALM. Hence, the CSA of psoas is useful for predicting survival and muscle mass in elderly patients with hip fractures.

Smartphone-Based Speech Therapy for Poststroke Dysarthria: Pilot Randomized Controlled Trial Evaluating Efficacy and Feasibility.

BACKGROUND: Dysarthria is a common poststroke speech disorder affecting communication and psychological well-being. Traditional speech therapy is effective but often poses challenges in terms of accessibility and patient adherence. Emerging smartphone-based therapies may offer promising alternatives for the treatment of poststroke dysarthria. OBJECTIVE: This study aimed to assess the efficacy and feasibility of smartphone-based speech therapy for improving speech intelligibility in patients with acute and early subacute poststroke dysarthria. This study also explored the impact of the intervention on psychological well-being, user experience, and overall feasibility in a clinical setting. METHODS: Participants were divided into 2 groups for this randomized, evaluator-blinded trial. The intervention group used a smartphone-based speech therapy app for 1 hour per day, 5 days per week, for 4 weeks, with guideline-based standard stroke care. The control group received standard guideline-based stroke care and rehabilitation. Speech intelligibility, psychological well-being, quality of life, and user acceptance were assessed using repeated measures ANOVA. RESULTS: In this study, 40 patients with poststroke dysarthria were enrolled, 32 of whom completed the trial (16 in each group). The intervention group showed significant improvements in speech intelligibility compared with the control group. This was evidenced by improvements from baseline (F1,30=34.35; P<.001), between-group differences (F1,30=6.18; P=.02), and notable time-by-group interactions (F1,30=6.91; P=.01). Regarding secondary outcomes, the intervention led to improvements in the percentage of correct consonants over time (F1,30=5.57; P=.03). In addition, significant reductions were noted in the severity of dysarthria in the intervention group over time (F1,30=21.18; P<.001), with a pronounced group effect (F1,30=5.52; P=.03) and time-by-group interaction (F1,30=5.29; P=.03). Regarding quality of life, significant improvements were observed as measured by the EQ-5D-3L questionnaire (F1,30=13.25; P<.001) and EQ-VAS (F1,30=7.74; P=.009) over time. The adherence rate to the smartphone-based app was 64%, with over half of the participants completing all the sessions. The usability of the app was rated high (system usability score 80.78). In addition, the intervention group reported increased self-efficacy in using the app compared with the control group (F1,30=10.81; P=.003). CONCLUSIONS: The smartphone-based speech therapy app significantly improved speech intelligibility, articulation, and quality of life in patients with poststroke dysarthria. These findings indicate that smartphone-based speech therapy can be a useful assistant device in the management of poststroke dysarthria, particularly in the acute and early subacute stroke stages. TRIAL REGISTRATION: ClinicalTrials.gov NCT05146765; https://clinicaltrials.gov/ct2/show/NCT05146765.

First report of Colletotrichum liaoningense causing anthracnose on winter squash in Korea.

Winter squash (Cucurbita maxima) is rich in vitamins C and B6 and is also a source of beta-carotene, a provitamin A carotenoid. About 13,000 tons have been produced annually in South Korea over the past 10 years. In the summer of 2022, severe rot was observed in winter squash for sale at a wholesale market in Jinju, South Korea, with approximately 10% of the 500 squashes observed affected. White fungal hyphae and dark orange spore masses were observed on the surface of the decayed squash. To isolate the causal agents, symptomatic tissues (3 × 3 mm) between diseased and healthy tissues per squash from 3 diseased squashes were excised, disinfested with 1% sodium hypochlorite for 20 s and 70% ethanol for 10 s, washed twice in sterilized distilled water, dried on sterilized filter paper, transferred to water agar, and incubated at 25°C for 2 days. Agar blocks (3 mm2) containing fungal colonies were transferred to potato dextrose agar (PDA) plates and incubated at 25°C until fungal colonies grew. Three isolates (GNU F137a‒c) with similar morphology were subcultured using the single-spore method. In PDA, the colonies looked like gray cotton when viewed from the front, were pale orange from the back, and numerous small black sclerotia-like grains could be observed on both sides. Setae were pale to medium brown, verrucose, 40-120 µm long, and 3-6 septated. Conidiophores were hyaline to pale brown, smooth-walled, septate, branched, and up to 45 µm long. Conidia were hyaline, smooth walled, aseptate, straight, cylindrical, the apex and base rounded, and 14-18 × 5-7 µm (n = 30). Appressoria were single, brown, aseptate, ellipsoidal to irregular in outline, with crenate margins, and 3.5-5 × 3-5 µm (n = 30). The morphological features of the fungal isolates matched descriptions of Colletotrichum species. To confirm the identity of the isolated fungus, genomic DNA of all three isolates was extracted using the Phire Plant Direct PCR Kit (Thermo Fisher Scientific, Baltics, UAB). The internal transcribed spacers (ITS) of the ribosomal RNA gene region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase 1 (CHS-1), histone H3 (HIS3), actin (ACT), and beta-tubulin (TUB2) genes were amplified and sequenced using the primer pairs ITS1/ITS4, GDF/GDR, CHS-79F/CHS-354R, CYLH3F/CYLH3R, ACT-512F/ACT-783R, and T1/T2, respectively. The sequences were deposited in GenBank (acc. nos., PP504320 and PP555649-PP555653). Concatenated sequences of the six genes obtained from isolates GNU F137a‒c and ex-types from each accepted taxon in previous studies were used to conduct a phylogenetic analysis using the maximum likelihood method in MEGA 11. The fungus isolated from winter squash was in the same clade as C. liaoningense. Therefore, the isolates were identified as C. liaoningense. For pathogenicity tests, three winter squash were wounded with a sterilized needle and inoculated with each isolate by injecting 100 µl conidial suspension (105 conidia/ml). Control squash were injected with sterilized distilled water. All treated squash were incubated at 25°C in the dark. The test was performed three times. All inoculated winter squash reproduced symptoms within 15 days, whereas the control squash were symptomless. The morphological characteristics and ITS sequence of the re-isolated strain matched those of the inoculated strain. To the best of our knowledge, this is the first report of fruit rot of winter squash in Korea and is even the first report on C. liaoningense in Korea. This disease is considered a post-harvest disease because no cases have yet been discovered in the field in Korea. This report will facilitate epidemiological research and the development of effective disease control strategies.

No increased risk of osteonecrosis of the jaw in osteoporotic patients with dental implants: a nationwide cohort study.

OBJECTIVES: The occurrence of implant-associated osteonecrosis of the jaw (ONJ) has been reported in osteoporotic patients, particularly in association with bisphosphonate therapy. This study aimed to investigate the risk of implant surgery and implant presence for ONJ occurrence in osteoporotic patients longitudinally. METHODS: Based on Korean National Health Information Database, subjects over the age of 65 who were diagnosed with osteoporosis between July 2014 and December 2016 were included. The implant group included subjects who had undergone dental implant surgery between January 2017 and December 2017, while the control group included those who had no history of dental implants. The primary outcome was the occurrence of ONJ, and the date of final follow-up was December 2020. RESULTS: A total of 332,728 subjects with osteoporosis were included in the analysis: 83,182 in the implant group and 249,546 in the control group. The risk of ONJ among those who had undergone implant surgery (risk of implant surgery-associated ONJ) was not higher than that among those without implant surgery. The risk of ONJ among those with implants (risk of implant presence-associated ONJ) was lower than that among those without implants. Even in subjects with a history of bisphosphonates, steroids, periodontitis, or tooth extraction, those who had undergone implant surgery or had implants did not have a higher ONJ risk than those who had not undergone surgery or did not have implants; rather, they showed a lower risk. CONCLUSIONS: The results may suggest that dental implants are not associated with an increased risk of ONJ. A further study on whether dental implants are associated with lower ONJ risk is needed. CLINICAL RELEVANCE: Dental implants did not increase the risk of ONJ development in osteoporotic patients, even with a history of bisphosphonates. This may suggest that the risk profiles for ONJ occurrence between selective insertion of dental implants and other dentoalveolar surgery associated with infectious conditions are different.

Intelligent Resource Allocation Scheme Using Reinforcement Learning for Efficient Data Transmission in VANET.

Vehicular ad hoc networks (VANETs) use multiple channels to communicate using wireless access in vehicular environment (WAVE) standards to provide a variety of vehicle-related applications. The current IEEE 802.11p WAVE communication channel structure is composed of one control channel (CCH) and several service channels (SCHs). SCHs are used for non-safety data transmission, while the CCH is used for broadcasting beacons, control, and safety. WAVE devices transmit data that alternate between CCHs and SCHs, and each channel is active for a duration called the CCH interval (CCHI) and SCH interval (SCHI), respectively. Currently, both intervals are fixed at 50 ms. However, fixed-length intervals cannot effectively respond to dynamically changing traffic loads. Additionally, when many vehicles are simultaneously using the limited channel resources for data transmission, the network performance significantly degrades due to numerous packet collisions. Herein, we propose an adaptive resource allocation technique for efficient data transmission. The technique dynamically adjusts the SCHI and CCHI to improve network performance. Moreover, to reduce data collisions and optimize the network's backoff distribution, the proposed scheme applies reinforcement learning (RL) to provide an intelligent channel access algorithm. The simulation results demonstrate that the proposed scheme can ensure high throughputs and low transmission delays.

User-Centric Cell-Free Massive MIMO with Low-Resolution ADCs for Massive Access.

This paper proposes a heuristic association algorithm between access points (APs) and user equipment (UE) in user-centric cell-free massive multiple-input-multiple-output (MIMO) systems, specifically targeting scenarios where UEs share the same frequency and time resources. The proposed algorithm prevents overserving APs and ensures the connectivity of all UEs, even when the number of UEs is significantly greater than the number of APs. Additionally, we assume the use of low-resolution analog-to-digital converters (ADCs) to reduce fronthaul capacity. While realistic massive access scenarios, such as those in Internet-of-Things (IoT) environments, often involve hundreds or thousands of UEs per AP using multiple access techniques to allocate different frequency and time resources, our study focuses on scenarios where UEs within each AP cluster share the same frequency and time resources to highlight the impact of pilot contamination in dense network environments. The proposed algorithm is validated through simulations, confirming that it guarantees the connection of all UEs and prevents overserving APs. Furthermore, we analyze the required fronthaul capacity based on quantization bits and confirm that the proposed algorithm outperforms existing algorithms in terms of SE and average SE performance for UEs.

Presurgical Reduction of the Cleft Palate: Serendipitous Benefit of the Stanford Orthodontic Airway Plate Treatment (SOAP) for Infants with Robin Sequence.

OBJECTIVE: Narrowing of the palatal cleft is often observed in infants with Robin sequence (RS) treated with the Stanford Orthodontic Airway Plate treatment (SOAP) even though SOAP is utilized primarily to establish airway patency. The current study quantified dimensional changes of the cleft palate (CP) in infants with RS treated with SOAP. DESIGN: A retrospective chart review. PATIENTS: Infants with RS and CP who completed SOAP and had maxillary arch models at both pre- and post-treatment time points at a single tertiary referral hospital between September 2019 and July 2023. SETTING AND OUTCOME MEASURE: Maxillary arch models were measured and analyzed using Bivariate statistical analysis. RESULTS: Seventeen infants were included in the study. The median age (min, max) was 6.7 weeks (1.1, 21.9) at pre-treatment and 26.6 weeks (18.7, 37.0) at post-treatment. The median Obstructive Apnea Hypopnea Index was 36.2 events/hour (8.1, 103.1) at pre-treatment and 4.1 events/hour (1.9, 8.6) at post-treatment. The pre-treatment width of CP decreased by an average (± standard diviation) of 6.37 mm (± 3.55, p < 0.001) at post-treatment. The ratio of the posterior cleft width to the total maxillary arch width decreased from 40% (± 9.1) at pre-treatment to 22% (± 11) at post-treatment (p < 0.001). CONCLUSION: The dimensions of CP reduced significantly during SOAP in infants with RS and CP treated for their severe upper airway obstruction. The findings highlight a potential benefit of SOAP that may contribute favorably to the palate repair surgery.

Comparison of the Surgical Outcome between the Multiple Screw Fixation and Fixed Angle Devices for the Basicervical Femoral Neck Fractures.

Introduction: Basicervical femoral neck fracture (FNF) is an uncommon type of femoral neck fracture and is associated with an increased risk of fixation failure due to its inherent instability. The purpose of this study was to compare the surgical parameters and reoperation rate between the use of a multiple cannulated screw (MCS) and fixed angle device (FAD) in treating basicervical FNFs. Methods: We retrospectively reviewed the records of 885 patients who underwent internal fixation between May 2004 and August 2019 to determine basicervical FNF with at least 12 months of follow-up. Among the identified 77 patients with basicervical FNF, 17 patients who underwent multiple cannulated screw (MCS) fixation and 36 patients who underwent fixed angle device (FAD) fixation were included. We compared the rates of fracture-site collapse and reoperations according to the fixation device. Results: Among the 53 patients with basicervical FNF, 13 patients (24.5%) sustained surgical complications (8 collapses of fracture site and 5 reoperations). The reoperation rate in the MCS group was significantly higher than that in the FAD group (23.5% vs. 2.8%, p = 0.016), without any significant difference in the collapse of the fracture site (11.8% vs. 16.7%, p = 0.642). Conclusions: Although basicervical FNF was rare among hip fractures, fracture site collapse was prevalent and prone to fixation failure. Surgeons should keep this in mind, and consider FAD for basicervical FNF.

Electron-Binding Dynamics of the Dipole-Bound State: Correlation Effect on the Autodetachment Dynamics.

The nature of the electron-binding forces in the dipole-bound states (DBS) of anions is interrogated through experimental and theoretical means by investigating the autodetachment dynamics from DBS Feshbach resonances of ortho-, meta-, and para-bromophenoxide (BrPhO-). Though the charge-dipole electrostatic potential has been widely regarded to be mainly responsible for the electron binding in DBS, the effect of nonclassical electron correlation has been conceived to be quite significant in terms of its static and/or dynamic contributions toward the binding of the excess electron to the neutral core. State-specific real-time autodetachment dynamics observed by picosecond time-resolved photoelectron velocity-map imaging spectroscopy reveal that the autodetachment processes from the DBS Feshbach resonances of BrPhO- anions cannot indeed be rationalized by the conventional charge-dipole potential. Specifically, the autodetachment lifetime is drastically lengthened depending on differently positioned Br-substitution, and this rate change cannot be explained within the framework of Fermi's golden rule based on the charge-dipole assumption. High-level ab initio quantum chemical calculations with EOM-EA-CCSD, which intrinsically takes into account electron correlations, generate more reasonable predictions on the binding energies than density functional theory (DFT) calculations, and semiclassical quantum dynamics simulations based on the EOM-EA-CCSD data excellently predict the trend in the autodetachment rates. These findings illustrate that static and dynamic properties of the excess electron in the DBS are strongly influenced by correlation interactions among electrons in the nonvalence orbital of the dipole-bound electron and highly polarizable valence orbitals of the bromine atom, which, in turn, dictate the interesting chemical fate of exotic anion species.

Dual adhesive unipolar polysaccharides synthesized by overlapping biosynthetic pathways in Agrobacterium tumefaciens.

Agrobacterium tumefaciens is a member of the Alphaproteobacteria that pathogenises plants and associates with biotic and abiotic surfaces via a single cellular pole. A. tumefaciens produces the unipolar polysaccharide (UPP) at the site of surface contact. UPP production is normally surface-contact inducible, but elevated levels of the second messenger cyclic diguanylate monophosphate (cdGMP) bypass this requirement. Multiple lines of evidence suggest that the UPP has a central polysaccharide component. Using an A. tumefaciens derivative with elevated cdGMP and mutationally disabled for other dispensable polysaccharides, a series of related genetic screens have identified a large number of genes involved in UPP biosynthesis, most of which are Wzx-Wzy-type polysaccharide biosynthetic components. Extensive analyses of UPP production in these mutants have revealed that the UPP is composed of two genetically, chemically, and spatially discrete forms of polysaccharide, and that each requires a specific Wzy-type polymerase. Other important biosynthetic, processing, and regulatory functions for UPP production are also revealed, some of which are common to both polysaccharides, and a subset of which are specific to each type. Many of the UPP genes identified are conserved among diverse rhizobia, whereas others are more lineage specific.

Pushing the Boundaries of Multicomponent Alloy Nanostructures: Hybrid Approach of Liquid Phase Separation and Selective Leaching Processes.

ConspectusAlloying, or mixing of multiple metallic elements, is the classical way of novel materials development since the Bronze age. Increased numbers of principal elements expand the compositional space for alloy design vastly, leading to nearly endless possibilities of unexpected and unique materials properties. In contrast to bulk alloying processes represented by casting of molten metal mixtures, the fabrication of multicomponent alloy (MCA) nanostructures such as nanoparticles and nanofoams with more than three elements is often challenging, and a few methodologies for directly synthesizing alloy nanostructures up to denary systems have been suggested recently. However, forming alloy nanoparticles inside another metal matrix, instead of inside aqueous media in wet-chemical synthesis, is a fairly well understood strategy in terms of physical metallurgy. Extracting those alloy nanophases from the matrix could provide an alternative way to fabricate novel MCA nanostructures.In this Account, we describe a hybrid approach of metallurgical bottom-up and chemical top-down processes for fabricating MCA nanostructures including nanoparticles and nanofoams. The former utilizes a liquid-state phase separation process that resembles "oil and water" but occurs at the nanoscale due to thermodynamic mixing relations among alloying elements and a rapid quenching process. Thermodynamic prediction of the immiscible boundary in a temperature-composition space (miscibility gap) plays a key role in designing precursor alloys for MCA nanostructures. Selective leaching, the chemical top-down process for extracting the alloy nanostructures from the precursors, uses the chemical reactivity difference between the embedded nanostructures and the matrix phase against a certain chemical solution. We discuss here that the precise control of alloy composition and cooling rate based on thermodynamic assessments enables researchers to prepare phase-separating precursor alloys for fabricating both nanoparticles and nanofoams with a broad size range from a few nanometers to a few hundred nanometers. Depending on the alloy systems, the atomic structure of alloy nanostructures could be controlled from fully amorphous to nanocrystalline and even to quasicrystalline structure. We demonstrate how the different sizes of alloy nanostructures fabricated by a single hybrid procedure can be effectively exploited for investigating size-dependent physical properties. The future and potential research directions for this hybrid approach are also briefly discussed. This unique approach for fabricating nanosized alloys provides an extended methodology to discover novel metallic nanomaterials with promising properties in diverse compositional spaces of MCA systems.

State-Specific Chemical Dynamics of the Nonvalence Bound State of the Molecular Anions.

Nonvalence bound states (NBS) are anionic states where the excess electron is extremely loosely bound to the neutral core through long-range potentials. In contrast to the valence orbitals of which the electron occupancy determines the molecular structure, as well as the chemical reactivity, the nonvalence orbital is quite diffuse and located far from the neutral core. The NBS can be classified into the dipole-bound state (DBS), quadruple-bound state (QBS), or correlation-bound state (CBS) according to the nature of the electron-neutral interaction, although their interaction potentials may cooperatively contribute. The NBS is ubiquitous in nature and has the strong implications in atmospheric, interstellar, or biological chemistry. Accordingly, NBS has long been conceived to play the role of the doorway into the formation of a stable anion or dissociative electron attachment (DEA). Despite intensive and extensive studies, however, the quantum-mechanical nature of NBS is still far from being thorough understanding. Herein, we describe a new aspect of state-specific NBS-mediated chemical dynamics, which has been revealed through a series of recent studies by our group. We have employed picosecond time-resolved pump-probe spectroscopy combined with cryogenically cooled ion trap and velocity-map imaging techniques to study closed-shell anions generated by electrospray ionization. DBS vibrational Feshbach resonances are prepared by the optical excitation of phenoxide, for instance, and their individual lifetimes have been precisely measured in a state-specific manner to reveal the strong mode-dependency of the autodetachment rate. Fermi's golden rule turns out to be extremely useful for a rational explanation of the experiment, although the more sophisticated theoretical model is desirable for the more quantitative analysis. For the DBS of para-chlorophenoxide or para-bromophenoxide where the polarizability of neutral core is substantial, the Fermi's golden rule based on the charge-dipole potential needs to be significantly modified to include the correlation effects to explain the exceptionally slow autodetachment rates. For the QBS of 4-cyanophenoxide, the mode-specific behavior of the quadrupole ellipsoid tensor explains the strong mode-dependent autodetachment rate. Meanwhile, the nonadiabatic transition of the excess electron into the valence orbital can result in stable anion formation or immediate chemical bond rupture. In the DBS of ortho-, meta-, or para-iodophenoxide, the transformation of the loosely bound excess electron into the πσ* antibonding orbital occurs to give I- as a final fragment. The fragmentation mediated by DBS occurs competitively with the concomitant autodetachment, paving a new way of the reaction control by tuning the quantum-mechanical nature of the DBS Feshbach resonance. This experimental observation provides the foremost evidence for the dynamic role of the DBS as a doorway into anion chemistry, such as DEA. The ponderomotive force on the electron in the nonvalence orbital has been demonstrated for the first time in a strong optical field, giving great promise for the manipulation of polyatomic molecules in terms of the spatial location, as well as the AC-Stark control of the chemical reaction.